Due to the aggressive scaling of CMOS components in the past years, parasitic resistances at the source and drain terminals of transistors have become an increasing problem. For reducing said parasitic resistances it is known to silicidate the electric contact surfaces in order to be able to use the entire surface of the semiconductor region to be contacted, e.g., the active source and drain region, as contact surface. As an example of the prior art, reference is made to J. Kedzierski et al., “Issues in NiSi-gated FDSOI device integration,” in IEDM Tech. Dig. 2003, who carry out such a silicidation of the source and drain contact surfaces.
The contact resistances of a silicidated electric contact surface between a semiconductor region and a metallic terminal element follow the equation:
      R    co    =            ρ      c              W      ·              l        c            
Pc represents the specific contact resistance between the metal surface and the silicon therebelow. W indicates the width of the contact and lc the contact length which, in the case of a transistor, corresponds to the expansion of the contact surface in channel direction of the transistor. The contact length lc has become a critical factor since the transistors have been scaled in the nanometer range. In addition, the specific contact resistance Pc depends on the surface doping concentration Nd and the Schottky barrier ΦB of the used metal or silicides.
      ρ    c    ∝      exp    ⁡          (                                    4            ⁢                                                  ⁢            π            ⁢                                                  ⁢                          Φ              B                                qh                ⁢                                                            m                *                            ⁢                              ɛ                Si                                                    N              d                                          )      
Wherein q denotes the elementary charge of an electron, m* the effective mass, ∈Si the dielectric constant of silicon, and h the Planck's constant. For further minimizing the contact resistances, experiments with alternative surface doping substances such as, e.g. sulfur, are currently carried out in order to reduce the specific contact resistance of the metal-silicon interface.
However, the introduction of new materials in a CMOS process involves considerable efforts and costs because the process normally becomes more complicated.